In the field of architectural design of avionics systems a tactical or combat unmanned vehicle is often used for scouting, exploring terrain or the like. Unmanned vehicles of all sorts (including aerial, ground, naval and underwater vehicles) need a so-called Contingency Planning (CP), in which CP refers to interim measures to recover the unmanned vehicle following an emergency or system disruption. Contingency Planning is usually done by the operator of the vehicle off-line (i.e. before a mission) and includes all information needed by the vehicle, in case of emergencies of any sort, to be able to perform in a proper way. Contingency planning covers all degrees of freedom (capabilities) of the vehicle and is normally very complex.
A typical emergency situation is failure of the communication data links. When so, the operator is unable to communicate with the vehicle anymore. The vehicle has to take actions autonomously, i.e. decide where to go, usually based on the instructions described in the contingency planning. Other contingencies may derive from failure that prevents the vehicle to complete the mission and reach the planned mission end point, e.g. failure of the propulsion system or the like. In this case the vehicle has to plan its way to alternate locations where it can safely terminate or shut down. This type of plans can usually be set up and changed by the operator of the unmanned vehicle if the data links are up and available but have to be issued autonomously if the data links are down.
Contingency Planning is a safety critical function that must be robust, predictable, deterministic and testable. On vehicles where safety is an issue, contingency planning has to be implemented with high software criticality levels, such as “Level A” referring to the document RTCA DO-178B. RTCA DO-178B is a document drawn up by Radio Technical Commission for Aeronautics that defines the guidelines for development of aviation software. In order to keep the development costs at an acceptable level the contingency planning should be kept at a very simple level.
Document US-A1 20040249519 discloses a system that prevents the unintentional uncontrolled flight of a radio control model airplane by providing an automated programmable flight control system based upon GPS navigation. In case of loss of transmitter power the model airplane would be directed by UAV components to a predetermined safe area such as back into the pilot's normal flight way.
Patent abstract of JP-A-2005-017027 discloses a method for providing an escape guiding system. A host device receives a request for escape guidance and information on the present position from a mobile phone with GPS functionality. A disaster information database and a map information database stored in a database are searched based on the positional information to find a less dangerous route to an escape area close to the position.
US-A1-2004/0193334 relates to remote control of an unmanned aerial vehicle, UAV. It flies according to a primary route and in occurrence of an emergency the UAV is controlled to fly an alternative route and if engine failure is detected the UAV is controlled to fly to a waypoint wherein it is safe to terminate the UAV flight.
Prior art solutions however are still rather complex and mission dependent. Thus there is a need for a simple reliable rerouting plan that is mission independent.
The general object of the invention is to provide an UAV that when said vehicle has to leave a planned route or mission path due to certain emergency contingencies, the unmanned vehicle knows where to move next in order to conclude the mission in the safest way. In short, a main object of the invention is to provide an emergency flight plan that is versatile, compact and does not require much computational power to be executed.
An aspect of this object is to provide a method for emergency navigation that does not need a lot of computational resources during the execution of the method.
A further object is to be able to pre-plan different complicated routes taking into account zones where the UAV is unable or not allowed to fly etc.
Another object is to provide a method that requires none, or a minimum of communication to the unmanned aerial vehicle.